Z86319 Datasheet, PDF (16/23 Pages) Zilog, Inc. – PS/2 MOUSE CONTROLLER

Z86319
PS/2 Mouse Controller
FUNCTIONAL DESCRIPTION (Continued)
Interrupts. The Z86319 features four interrupts from
four different sources. These interrupts are maskable and
prioritized (Figure 17). The four sources are divided as fol-
lows: the falling edge of P31, P33, and the two
counter/timers. The Interrupt Mask Register globally or in-
dividually enables or disables the four interrupt requests
(Table 5).
When more than one interrupt is pending, priorities are re-
solved by a programmable priority encoder that is con-
trolled by the Interrupt Priority register. All Z86319 inter-
rupts are vectored through locations in program memory.
When an interrupt machine cycle is activated, an interrupt
request is granted, thereby disabling all subsequent inter-
rupts, saving the Program Counter and Status Flags, and
branching to the program memory vector location reserved
Zilog
for that interrupt. This memory location and the next byte
contain the 16-bit starting address of the Interrupt Service
Routine for that particular interrupt request.
To accommodate polled interrupt systems, interrupt inputs
are masked and the Interrupt Request Register is polled to
determine which of the interrupt requests requires service.
Table 5. Interrupt Types, Sources, and Vectors
Source
P33
P31
T0
T1
Name
IRQ1
IRQ2
IRQ4
IRQ5
Vector
2,3
4,5
8,9
10,11
Location Comments
External
External
Internal
Internal
Falling Edge
Falling Edge
IRQ1 - IRQ5
IRQ
IMR
6
Interrupt
Request
Global
Interrupt
Enable
IPR
Priority
Logic
Vector Select
Figure 17. Interrupt Block Diagram
16
PRELIMINARY
DS97KEY1605